In the prior art, there exists the multilayer wiring substrate for mounting a semiconductor chip. In the multilayer wiring substrate, the build-up wiring is formed on both surface sides of the core substrate, and also the chip connection pads for mounting the semiconductor chip are provided on one surface and the external connection pads are provided on the other surface.
In Patent Literature 1 (Japanese Laid-open Patent Publication No. 2004-273480), it is set forth that the wiring substrate is constructed based on such a manner that the conductive material is buried in the through holes, which are located in the area where the electrodes are arranged, out of a large number of through holes in the porous oxidized aluminum formed by the anodic oxidizing method, whereas the insulating material is buried in the through holes located in the area except it.
In Patent Literature 2 (Japanese Laid-open Patent Publication No. 2009-147241), it is set forth that the circuit substrate is constructed by forming the insulating layer, in which the opening portions to expose the selected through-hole conductors are provided, on both surfaces of the porous alumina substrate having a plurality of through-hole conductors, and then forming the wirings which are connected to the through-hole conductors in the opening portions.
As described later, in the related art, the wiring substrate is manufactured based on such a manner that the build-up wiring is formed on the thin oxidized aluminum substrate in which a large number of penetration conductors are provided. The oxidized aluminum substrate including a large number of penetration conductors is in a fragile condition because rigidity of the substrate is weak.
As a result, when the build-up wiring layer is formed on the oxidized aluminum substrate, cracks easily occur in the oxidized aluminum substrate.
Also, the fine penetration conductors are provided up to the edge part of the oxidized aluminum substrate. As a result, when a mechanical impact is given during the manufacturing step, or the like, in some cases the penetration conductors fall to peel off from the edge part of the oxidized aluminum substrate.